hey im new to the ar15 i just picked up my first one its a bushmaster xm15
what are some basic things i can do to upgrade it? thanks

What are you using it for?  What do you want/expect from it?  

Use will determine what the appropriate upgrades are.  

Is it going to be used for HD?  SHTF?  Patrol/duty?  Range gun/plinker?  

Make sure you gain proficiency with the irons before you start spending massive amounts of money on optics.  

Learn the weapon system front and back, and it will make it easier for you to determine what upgrades are necessary, and which are not.

For 95% of people, a stock, factory AR will be sufficient, and need no active upgrades.  Some upgrades improve function, some specialize the weapon, some will improve reliability, some improve comfort or utility, some offer tactical benefits, some offer competition benefits, some don't offer benefits at all.  

Some look cool, some look like shit, some you'll never even notice, most of the ones on the market are a waste of money, but some are great investments.  

HTH,
~Augee

One of the first upgrades I did was the grip. The stock grip is crap to me. I switched to the Ergo grip but only after trying it out on another members AR. The Hogue grips are nice also and I have one on my wife's rifle. If you have larger hands, the Ergo is nice. There are several options for grips and if you can try 'em before you buy 'em it helps.

As far as the rest of the rifle, keep it stock until you get used to it. Master iron sights before going to an optic like an Eotech, Aimpoint, ACOG.